Expose packet loss counts from QUIC to NetworkQualityEstimator

net/base/socket_performance_watcher.h

Index: net/base/socket_performance_watcher.h
diff --git a/net/base/socket_performance_watcher.h b/net/base/socket_performance_watcher.h
index e0e76327ce63541e8d0dc2ba23215d34f953df41..eee526512820c58ff651ff8de5f34a0050ba79a0 100644
--- a/net/base/socket_performance_watcher.h
+++ b/net/base/socket_performance_watcher.h
@@ -5,6 +5,8 @@
 #ifndef NET_BASE_SOCKET_PERFORMANCE_WATCHER_H_
 #define NET_BASE_SOCKET_PERFORMANCE_WATCHER_H_
 
+#include <stddef.h>
+
 #include "base/macros.h"
 #include "net/base/net_export.h"
 #include "net/base/socket_performance_watcher_factory.h"
@@ -33,6 +35,22 @@ class NET_EXPORT_PRIVATE SocketPerformanceWatcher {
   // made, hence no timestamp.
   void OnUpdatedRTTAvailable(const base::TimeDelta& rtt) const;
 
+  // Called when the incremental packet counts at the transport layer are
+  // available. All the counts are since the last call to the
+  // OnIncrementalPacketCountAvailable. This method is called immediately after
+  // the observation is made, hence no timestamp.
+
+  // An example:
+  // Last observation after packet #1. Packets #5 and #6 are received:
+  //   missing = 3, in_order = 2, out_of_order = 0.
+
+  // Last observation after packet #6. Packet #3 received:
+  //   missing = 0, in_order = 0, out_of_order = 1.
+  void OnIncrementalPacketCountAvailable(
+      size_t packets_missing,
+      size_t packets_received_in_order,
+      size_t packets_received_out_of_order) const;
+
  private:
   // Transport layer protocol used by the socket that |this| is watching.
   const SocketPerformanceWatcherFactory::Protocol protocol_;